[Glenn]

Hi,

I have a subpanel where the ground and neutral are the same bar. My understanding is ground and neutral can be the same in the main panel, but must be separated in a subpanel.

What are the ramifications of the fact that the subpanel is not wired correctly? Should it be rewired. It's an older box, and there is no separate ground and neutral. I'd have to replace the subpanel. I'm going to be adding a 220v hot tub to it.

Thanks,

Glenn

[tkrussell]

Could be the panel was installed with a 3 wire feeder back when it was allowed. I canot remember when that was.

If at all possible, a 4 wire feeder should be installed and separate the neutral and grounds at the subpanel.

The issue is twofold, A neutral is a current carrying conductor, and an equipment ground, under normal conditions, is not. The equipment ground is reserved for fault currents.

[Missouri Bound]

Well the current code wouldn't accept it, but it's possible that the inspector will allow it under a "grandfather" type issue. You are getting a permit, right? Your town or more accurately the electrical inspector has the final say in this matter. It's not an issue as far as safety so there really is no concern there. But some municipalities require a "brought up to code" update when the project is of sufficient magnitude.

[stanfortyman]

Could be the panel was installed with a 3 wire feeder back when it was allowed. I canot remember when that was.

This was a very recent change. It was allowed under the 2005 NEC and removed/changed in the 2008 edition.
NEC 250.32

[tkrussell]

That recent huh? I never knew panels were allowed to have a 3 wire feeder until I started answering questions and looking in the Code for things I never dealt with.

I was installing 4 wire feeders for "subpanels" long before that, late 70's.

Only installed 3 wire feeders for ranges and dryers, as that was the norm in the industry. Never liked it thou, very glad the Code made that change eventually.

Glenn, Missouri makes a good point, see if the local inspector will allow it to remain, if you like.

Me personally, I would be giving you a price to upgrade it to a 4 wire, even if it it allowed.

[Glenn]

Thanks for the responses. The house was renovated in 1978, so maybe code allowed 3-wires to the subpanel then. The subpanel is on the outside of the house, on the other side of the house from the main panel. It would be a bear to run 4-wire through the house, it's all underneath finished drywall. I guess I could run a 4-wire in conduit around the outside of the house.

I wasn't planning on getting a permit. I did plug the hot tub into the subpanel temporarily, and everything on the subpanel ran fine together. I will be putting a 50-amp breaker in the sub-panel and 50-amp CGFI at the service box near the hot tub. Will the CGFI perform correctly with only 3 wires?

What about this as a solution? Can I replace the 3-wire subpanel with a new 4-wire subpanel (separate neutral and ground). Rewire the 2 hots and neutral to it, and drive a copper wire and stake into the ground outside right at the sub-panel. This gives me separate ground and neutral without having to run new 4-wire from mail panel.

Thanks.

[tkrussell]

No driving a ground rod is not allowed,as it would serve no purpose.

[stanfortyman]

What about this as a solution? Can I replace the 3-wire subpanel with a new 4-wire subpanel (separate neutral and ground). Rewire the 2 hots and neutral to it, and drive a copper wire and stake into the ground outside right at the sub-panel. This gives me separate ground and neutral without having to run new 4-wire from mail panel.

Thanks.

This is a very common misconception, and TK is completely correct.

Driving a rod into the ground is a completely different "ground" than a circuit ground or equipment ground.
A circuit or equipment ground does not come from the earth or have anything to do with a grounding electrode. It comes from the neutral bond in the main service enclosure.